1. Field of the Disclosure
The present application relates to an organic light emitting diode (OLED) display device. More particularly, the present application relates to a manufacturing method of an organic light emitting display device adapted to enhance the performance of an oxide thin film transistor by reducing a hydrogen content within a passivation layer.
2. Description of the Related Art
Image display devices realizing a variety of information on screens correspond to a core technology of the information communication age. As such, the image display devices are being developed in such a manner as to be more thin and light and portable and have high performance. Moreover, flexible display devices are being required in order to enhance convenience of users and spatiality. In view of these points, OLED display devices controlling alight emitting quantity of an organic emission layer come into the spotlight as flat panel display devices.
The OLED display device includes: a thin film transistor array formed on a substrate; organic light emitting cells disposed over the thin film transistor array; and a glass cap used to isolate from the exterior. Such an OLED display device uses an electroluminescent phenomenon. In other words, The OLED display device emits light by enabling excitons within an organic emission layer to transition from an excitation state to a ground (a base) state. The excitons are formed through recombination of electrons and holes which are injected from an electron injection electrode and a hole injection electrodes into the organic emission layer when an electric field is applied between anode and cathode electrodes on both sides of the organic emission layer.
In detail, the OLED display device includes a plurality of sub-pixels arranged pixel regions which are defined by gate lines and data lines crossing each other. Each of the sub-pixels receives a data signal from the respective data line when a gate pulse is applied from the respective gate line. Also, each of the sub-pixels emits light corresponding to the received data signal. Such a sub-pixel includes: a thin film transistor formed on the substrate; and an organic light emitting cell connected to the thin film transistor.
FIG. 1 is a cross-sectional view showing a pixel region of a general OLED display device.
Referring to FIG. 1, the OLED display device 100 includes: an array layer 103 formed on a substrate 101; an organic light emitting diode (OLED) layer 105 formed on the array layer 103; a passivation layer 106 configured to encompass the OLED layer 105; and an adhesive layer 107 and a sealing layer 110 formed on the passivation layer 106. The array layer 103 includes thin film transistors, gate lines, data lines and power lines which are formed on the substrate 101. The OLED layer 105 includes electrodes and organic emission layer.
The passivation layer 106 is formed by depositing a SiN-based or SiO-based compound on the substrate 101 (i.e., on the OLED layer 105) using a PECVD (plasma enhanced chemical vapor deposition) method.
However, in order to prevent deterioration of the organic emission layer within the OLED layer 105, the formation process of the passivation layer 106 must be performed under a low temperature status below 100° C. Due to this, a large quantity of hydrogen included into SiH4-based and NH3-based gases must remain in the passivation layer 106.
The hydrogen remaining in the passivation layer 106 is drifted toward the array layer 103 under the passivation layer 106 as time passes. Also, the drifted hydrogen H deoxidizes an oxide semiconductor layer (a channel layer) of the thin film transistor within the array layer 103. As such, the performance of the thin film transistor must deteriorate.
In other words, the residual hydrogen H in the passivation layer 106 shifts a threshold voltage Vth of the thin film transistor. As such, faults such as a screen stain and non-uniformity of brightness are generated.